Yes, an employee is entitled to accrue her normal annual leave in addition to public holidays during the 16 weeks of additional unpaid maternity leave.
Maternity leave is not dependent on an employee returning to work and an employee who intednds to return to work must give formal notice of that intention at least four weeks before her ML or additional ML is due to end. Employees are entitled to all rights under the Maternity Protection Act whether they intend to return to work or not.